Horseshoe Lake: 8/28/00 Transect began at culvert under paved road SE of Lake and went up the drainage to north park boundary fence.
Parking Lot J: 8/26//00 From park road north to base of bluff.
Salmon Hole: 8/30/00 From park road at Salmon Hole parking lot north to boundary fence.
East end of park: 9/1/00 From turnaround north near boundary fence to base of upper bluff.
“Sapling”: <6″ diameter (non-reproductive) but >1 meter in height
“Alive”: green leaves on root crown sprouts and/or green leaves on upper branches
“Dead”: no sign of green leaves.
Blue Oaks. Since the saplings readily send up root crown sprouts if the top dies, only 2% of them died. Most of the dead mature oaks appeared to have been injured at the base in previous fires and dead dry wood there (with no protective bark) burned very hot over some length of time. The thick bark on the mature trees protects them as long as it remains intact and the exposure time to heat is limited.
Interior Live Oak. Since both mature and sapling live oaks produce root crown sprouts, these trees survived very well (2.1% died). Both the older and younger branches have a thin bark that is easily killed by heat so many of the above ground branches were dead. From a distance, one has the impression that the trees are completely dead but a closer view reveals vigorous, 4-foot-high root crown sprouts. Each fire therefore stimulates a new ring of branches from the root crown; in some areas these rings are 6 feet in diameter and suggest that the original plant is now hundreds of years old having produced a succession of “fire rings”.
Foothill Pine. These plants are loaded with flammable hydrocarbons that bum with a burst of flame that kills the young plants. The older plants have a thick bark that protects their trunks and usually their lower branches are high above the flames having been burned in previous fires. However, when a fire has left dead wood at the base, then it may bum for a sufficient time to kill the tree. Without root crown burls, the young trees have a high mortality. In a high fire environment, these pines have other strategies for survival. Large seeds with fire-resistant seed coats stored deep within a tough cone is the main one. Another is rapid growth (30″ per year is common) and early prolific production of seeds (12 to 16 years). Jays and squirrels bury great numbers of seeds and so the species is doing well.
Shrubs that do not crown sprout. Only 2 of the 12 species of shrubs found here do not produce crown sprouts when the top is killed; therefore both have a high mortality (35.4% combined). In this fire-prone environment, they depend on fire to stimulate germination for species survival. For example, under a burned pine tree above Horseshoe Lake one can find over a thousand buckbrush seedlings, now 4-6″ high, from seeds of the dead parent plants nearby. Manzanita also depends on fire to stimulate seed germination.
Shrubs that produce root crown sprouts. The remaining 10 kinds of shrubs (like Toyon, coffeeberry, and redberry) all produce root crown sprouts and only 1.7% out of 458 died in these transects. This is dramatic evidence of the value of root crown sprouting in a high fee environment.
Other observations. Since most of the mature trees died from fire taking hold in dead wood at the base (from previous fires) or accumulation of fuel on the upslope side of the trunk, it seems quite evident that if woody debris could be removed from near the trunk of a tree, either by periodic low-intensity fires or mechanically, that tree would have a much better chance for survival. Keeping fire from an area for a long period of time would seem to be a sure way to wreak destruction when fire finally came. Furthermore it would prevent the germination of seeds of species like buckbrush and manzanita. Buckbrush has nitrogen-fixing bacteria on its roots and contributes greatly to the supply of nitrogen for all its neighbors.
What has not been addressed is the benefit of the fire to our native bunch grasses (deer grass and purple needle grass). These have growing points below ground and survive by crown sprouting better than blue and live oak. Also, all those perennials with bulbs, corms and rhizomes below ground survived and benefited from the nutrients made available by the fire; these include brodiaea, lily, iris, sedge, mariposa, and many others. As the Native Americans showed us, they benefit from fire every year. In addition to making available elements like potassium and phosphorous, fire kills billions of microorganisms in the upper inch or two of soil. They are rich in nitrogen, in particular, which becomes rapidly available to the plants that get there first (like those that crown sprout).
Conclusions. In this plant community we should expect periodic fires; in fact, the present mix of plants requires it. Keeping fires under control and allowing burning under cool, low-wind, high humidity conditions (as generally occurred in this fire) seems a practical way to manage fire in this park.
|Horseshoe Lake||Parking Lot J||Salmon Hole||East End of Road||Total||Total||Percent dead|